Electrical field stimulation (EFS) of the rabbit ileum mounted in a flux chamber increases the transmural electrical potential difference and the short circuit current, and causes secretion of Cl ion by enhancing the flux of Cl ion from the serosal to the mucosal surface. All these changes are prevented when the tissue is exposed to a concentration of the neurotoxin, tetrodotoxin (10 to the minus 7th power M). In addition, tetrodotoxin acting alone, increases the absorption of Na and Cl by augumenting their mucosal to serosal movement. The mechanism by which EFS causes Cl secretion is not known. I will investigate that mechanism by determining: 1) whether the intracellular epithelial concentrations of cyclic adenosine monophosphate are increased by EFS; 2) how the responses to EFS are altered by agents that affect the responses of epithelial cells to vasoactive intestinal peptide (VIP) such as somatostatin and beta-lactamimide; 3) the effect of effective serotonin antagonists on the responses to EFS, e.g., mianserin HCL; 4) the effects of different square wave frequencies of EFS. I will also try to determine the way in which tetrodotoxin acts to increase the absorption of Na and Cl, because this may be intimately related to the effects of EFS on electrolyte transport and its electrical characteristics.